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//
// G4StatAnalysis
//
// Class description:
//
//  Class for statistical analysis of random variable
//
//  Adapted from:
//  Lux, I.
//      Monte Carlo particle transport methods: neutron and photon
//      calculations/authors, Ivan Lux and Laszlo Koblinger.
//      ISBN 0-8493-6074-9
//  1. Neutron transport theory. 2. Photon transport theory.
//  3. Monte Carlo method. I. Koblinger, Laszlo. II. Title.
//     QC793.5.N4628L88 1990 530.1 '38'20

// Author: J.Madsen, 25.10.2018
// --------------------------------------------------------------------
#ifndef G4StatAnalysis_hh
#define G4StatAnalysis_hh 1

#include <cmath>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <limits>
#include <optional>

#include "globals.hh"
#include "tls.hh"

#include "G4Allocator.hh"
#include "G4Timer.hh"
#include "G4Types.hh"
#include "G4ios.hh"

class G4StatAnalysis
{
 public:
  inline G4StatAnalysis();
  inline ~G4StatAnalysis() {}

  // Accumulated values
  inline G4double GetMean() const;
  inline const G4double& GetSum() const;
  inline const G4double& GetSumSquared() const;
  inline const G4double& GetSum1() const;
  inline const G4double& GetSum2() const;
  inline const G4int& GetHits() const;
  inline G4int GetNumNonZero() const;
  inline G4int GetNumZero() const;

  // Some control over accumulated variables
  inline void SetSum(const G4double& val);
  inline void SetSumSquared(const G4double& val);
  inline void SetSum1(const G4double& val);
  inline void SetSum2(const G4double& val);
  inline void SetHits(const G4int& val);
  inline void SetZero(const G4int& val);

  // Computed values
  inline G4double GetFOM() const;
  inline G4double GetRelativeError() const;
  inline G4double GetStdDev() const;
  inline G4double GetVariance() const;
  inline G4double GetCoeffVariation() const;
  inline G4double GetEfficiency() const;
  inline G4double GetR2Int() const;
  inline G4double GetR2Eff() const;

  // Conversion
  inline operator G4double() const;

  // Modifications
  inline void Reset();
  inline void Add(const G4double& _val, const G4double& _weight = 1.0);
  inline void Rescale(const G4double& factor);

  // Output
  inline void PrintInfo(std::ostream& os, const std::string& = "") const;

  // Operators
  inline G4StatAnalysis& operator+=(const G4double& _val);
  inline G4StatAnalysis& operator/=(const G4double& _val);
  inline G4StatAnalysis& operator+=(const G4StatAnalysis&);
  inline G4StatAnalysis& operator-=(const G4StatAnalysis&);

  // Allocators
  inline void* operator new(std::size_t);
  inline void operator delete(void*);

  // Timing (member functions)
  inline G4double GetCpuTime() const;
  // Timing (static functions)
  static tms* GetCpuClock()
  {
    G4ThreadLocalStatic std::optional<tms> _instance(std::nullopt);
    if(_instance == std::nullopt)
    {
      _instance = tms();
      times(&_instance.value());
    }
    return &_instance.value();
  }
  // Note: this above implementation was implemented in such a way as to
  // conserve memory by eliminated every instance from requiring their own
  // timing variables. The ResetCpuClock function below is called at the
  // beginning of the run (G4Run constructor) to attempt to ensure the
  // FOM is not skewed by multiple runs -- it may be necessary to
  // manually invoke in some situations
  static void ResetCpuClock()
  {
    tms* _clock = GetCpuClock();
    times(_clock);
  }

  // friend operator for output
  friend std::ostream& operator<<(std::ostream& os, const G4StatAnalysis& obj)
  {
    obj.PrintInfo(os);
    return os;
  }
  // friend operator for addition
  friend const G4StatAnalysis operator+(const G4StatAnalysis& lhs,
                                        const G4StatAnalysis& rhs)
  {
    return G4StatAnalysis(lhs) += rhs;
  }
  // friend operator for subtraction
  friend const G4StatAnalysis operator-(const G4StatAnalysis& lhs,
                                        const G4StatAnalysis& rhs)
  {
    return G4StatAnalysis(lhs) -= rhs;
  }

 private:
  G4double fSum1 = 0.0;  // summation of each history^1
  G4double fSum2 = 0.0;  // summation from each history^2
  G4int fHits    = 0;    // number of scoring histories
  G4int fZero    = 0;    // number of histories that were not greater than 0.0
};

#include "G4StatAnalysis.icc"

#endif